A vacuum cleaner typically comprises a main body containing dirt and dust separating apparatus, a floor tool connected to the main body and having a suction opening, and a motor-driven fan unit for drawing dirt-bearing air through the suction opening. The suction opening is directed downwardly to face the floor surface to be cleaned. The dirt-bearing air is conveyed to the separating apparatus so that dirt and dust can be separated from the air before the air is expelled to the atmosphere. The separating apparatus can take the form of a filter, a filter bag or, as is known, a cyclonic arrangement. The present invention is not concerned with the nature of the separating apparatus and is therefore applicable to vacuum cleaners utilizing any of the above arrangements or another suitable separating apparatus.
A driven agitator, usually in the form of a brush bar, is supported in the floor tool so as to protrude by a small extent from the suction opening. The brush bar is activated mainly when the vacuum cleaner is used to clean carpeted surfaces. The brush bar comprises an elongate cylindrical core bearing bristles which extend radially outward from the core.
Rotation of the brush bar may be driven by an electric motor powered by a power supply derived from the main body of the cleaner, or by an air turbine assembly driven by an air flow into the floor tool. The rotation of the brush bar causes the bristles to sweep along the surface of the carpet to be cleaned to loosen dirt and dust, and pick up debris. The suction of air generated by the fan unit of the vacuum cleaner causes air to flow underneath the floor tool and around the brush bar to help lift the dirt and dust from the surface of the carpet and then carry it from the suction opening through the floor tool towards the separating apparatus.
When the floor tool is to be used to clean a hard floor surface, it is desirable to stop the rotation of the brush bar to prevent the floor surface from becoming scratched or otherwise marked by the moving bristles of the brush bar. When the brush bar is driven by a motor, a switch may be provided on the floor tool to enable a user to de-activate the motor driving the rotation of the brush bar before the floor tool is moved on to the hard floor surface. Alternatively, a sensor may be provided on the bottom surface of the floor tool for detecting the type of floor surface upon which the floor tool has been located, and for deactivating the motor depending on the detected type of floor surface.
WO2004/028330 describes a mechanism for allowing a user to stop the rotation of a brush bar driven by an air turbine assembly. The turbine assembly comprises a vaned impeller which is mounted within a housing for rotation relative to a guide vane plate. The housing is located on one side of the floor tool. The impeller is connected to the brush bar by a pulley system. The housing has an air outlet connected to a suction duct extending between the suction opening and the main body of the vacuum cleaning appliance, and an air inlet for admitting ambient air into the housing. When the appliance is switched on, ambient air is drawn through the housing, causing the impeller to rotate and drive the rotation of the brush bar.
The mechanism comprises a movable button which is connected to the inlet side of the housing by an annular diaphragm seal. The seal is connected to a cylindrical outer wall of an inlet cap located over the air inlet of the housing. The inlet cap has a conical inner wall which defines with the button and the seal an airflow path for conveying air towards the vanes of the guide vane plate and the impeller. The button, inlet cap and guide vane plate define a pressure chamber which contains a spring for urging the button away from the guide vane plate. The guide vane plate comprises apertures which allow air to be evacuated from the pressure chamber through rotation of the impeller relative to the guide vane plate.
To stop the rotation of the brush bar, the user depresses the button to urge the seal against the inner wall of the inlet cap to block the air flow to the vanes. The lack of air flow through the housing causes the impeller and the brush bar to come to rest. The pressure chamber becomes evacuated under the pumping action of the fan of the vacuum cleaning appliance. The force acting on the button due to the pressure differential between the air inside the pressure chamber and the ambient air gradually becomes greater than the opposing force of the spring, with the result that when the user releases the button the seal remains urged against the inlet cap.
To restart the rotation of the brush bar during cleaning, the user opens a valve to admit air into the airflow downstream from the turbine assembly. This valve may be a suction release trigger located on a wand to which the floor tool is attached. Opening the valve lowers the pressure difference across the button to allow the spring to push the button away from the inlet cap to open the airflow path through the turbine assembly and restart the rotation of the impeller.
The stopping and re-starting of the brush bar thus requires two different user operations; to stop the brush bar the user must depress the button, whereas to re-start the brush bar the user must operate the suction release trigger on the wand. Furthermore, the depression of the button can be inconvenient for the user. The user has to either bend down to depress the button, or invert the wand to raise the floor tool towards hand or eye level.